Winsock is a programming interface and the supporting program that handles input/output requests for Internet applications in a Windows operating system. It's called Winsock because it's an adaptation for Windows of the Berkeley UNIX sockets interface. Sockets is a particular convention for connecting with and exchanging data between two program processes within the same computer or across a network.

Winsock runs between an application program such as a Netscape browser and the Internet program in your computer that uses TCP/IP. A request flows in the following order:

Web browser or other application
TCP/IP layers
Modem or network card
The Internet and destination

Winsock provides this interface for different versions of the Windows operating system. A comparable interface exists for Mac computers. Beginning with Windows 95, Winsock came as part of the operating system, but in earlier systems, a Winsock program had to be installed. UNIX systems do not require a Winsock equivalent because TCP/IP and its use of sockets was designed to run directly with UNIX application programs.

A number of companies offer a Winsock program, sometimes along with a suite of Internet protocol programs and applications. For example, Chameleon offers a suite that includes a Web browser, an FTP utility, a mail utility, and others. The Winsock program is included. The Trumpet Winsock is another popular stand-alone version. Winsock runs as a Windows dynamic link library (DLL) file. That is, it is loaded into the computer when an application needs it but doesn't need to be included as part of the application.

If you have an older computer, when you initially get set up with Internet access, you may need to make sure you have the right version of Winsock for your operating system and the applications provided by the access provider. If your operating system provides one version and the application suite provided by the access provider provides another, one version of Winsock may need to be removed.

This was last updated in September 2005

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